Steven Pacala

In An Inconvenient Truth (pp. 280-281), Al Gore enthused about a Science magazine study by Princeton economists Robert Socolow and Stephen Pacala. The study concluded that, “Humanity already possesses the fundamental scientific, technical, and industrial know how to solve the carbon and climate problems for the next half century.” Gore claimed the policies Socolow and Pacala recommend, “all of which are based on already-existing, affordable technologies,” could reduce emissions below 1970s levels.

But Gore could not know the solutions are “affordable,” because the authors did not attempt to estimate costs. The study basically shows that if political leaders can somehow coerce everybody to use less energy and adopt low- or zero-carbon energy technologies regardless of cost, they can significantly reduce emissions by 2054. We needed Princeton professors to tell us that?

If An Inconvenient Truth were a balanced presentation rather than a CGI-embellished lawyer’s brief, Gore would have mentioned that Socolow and Pacala’s (S&P) study was a response to an earlier analysis, also published in Science, by New York University Prof. Martin Hoffert and 17 colleagues.

Hoffert et al. found that all existing energy technologies “have severe deficiencies that limit their ability to stabilize global climate.” They specificially took issue with the UN IPCC’s claim that “known technological options” could stabilize atmospheric carbon dioxide (CO2) levels at 550 parts per million (ppm) or even 450 ppm over the next 100 years. Noting that world energy demand could triple by 2050, they found that zero-carbon technologies that can produce 100 to 300% of present world power consumption “do not exist operationally or as pilot plants.” Bottom line: “CO2 is a combustion byproduct vital to how civilization is powered; it cannot be regulated away.” They concluded that it is not possible to stabilize atmospheric CO2 concentrations and meet global energy needs “without drastic technological breakthroughs.”

I review this ancient history because Environmental Research Letters just published a study ‘updating’ (i.e. rebutting) the S&P analysis. The lead author is UC Irvine Prof. Steven Davis. One of three other co-authors is Martin Hoffert.

S&P estimated that seven “stabilization wedges” could limit atmospheric CO2 concentrations to 500 ppm by 2054. The Davis team estimates it will take 19 and possibly 31 wedges to solve the climate ‘problem.’ In other words, the challenge is much more difficult than S&P believed.